Thermal cut-out



INVENTOR MGUPi'YS J: @andin,

Fig.5.

M. J. SANDIN THERMAL CUT-OUT Original Filed Jan. 25, 1925 Get 192s.

WITNESSES:

ATTORNEY Patented a. 2, 1928.

UNITED STATES MAURTTS J. SANDIN, OF WILKINSBURG,

PATENT (OFFICE.

PENNSYLVANIA, ASSIGNOR TO WESTING- VANIA.

THERMAL CUT-OUT.

App11cation filed January 23, 1923, Serial No. 614,378. Renewed September 18, 1926.

I My invention relates to thermal cutouts and particularly to circuit-interrupting cutouts of the plug type adapted for use in standard socket receptacles. In my copending application for thermal cutouts, Serial N 0. 614,37 9, filed January 23,

The construction disclosed in the above 00- pending application is designed for operation' in circuits carrying a definite range of current and is particularly adapted for use where the current exceeds approximately five amperes. An object of my present invention is to provide a thermal-responsive cutout similar in character to that'illustrated in the above-mentioned application but which is designed for carrying heavier currents or for carrying similar currents for a longer period of time.

Another object of my invention is to provide a cutout device wherein the refill is of simple and inexpensive construction and which may readily be replaced within the plug receptacle.

Another object of my invention is to provide a cutout device, having the above characteristics, wherein a heat-absorbing member surrounds the heating conductor of the refill or thermal-responsive element for rendering the heating conductor capable of carrying heavier currents for a conductor of predetermined size and wherein the time characteristics of the thermal-responsive element may be varied by using heat-absorbing members of different proportions.

Another object of my invention is to provide a cutout device wherein the heatabsorbing member is in the form of a tube which fits over the heating conductor of the refill and is adapted to be moved longitudinally thereof when. the members of the refill are released and to move over the released end of the heating conductor for the purpose of cooling and snufling out the arcincident to the separation of the members of the refill.

Another object of my invention is to provide a cutout device wherein the terminals and plug receptacle are so protected from the heated arc gases that no injury can be done thereto, therefore rendering the device capable of repeated use. i

These and other objects,that will be made apparent throughout the further description of my mvention, are attained by means of the apparatus hereinafter described, and illustrated III the accompanying drawings, where- 1112 Figure 1 is a longitudinal sectional view of a cutout device embodying features of my invention;

Fig. 2 is an end view of the device shown in Fig. 1 with the cover removed;

Fig. 3 is a transverse section through the device taken on the line III-III of Fig. 1;

Fig. 4.- is a longitudinal section through a modified form of cutout device, and

Fig. 5 is a longitudinal section through a further modification of the device.

. Referring to the drawings, the device in- .cludes an insulating casing 6, preferably made of porcelain or insulating compound, having one end closed and provided with bores 7 and 8, the latter being of greater diameter than .the former. A tubular terminal 9 is secured to the closed end of the casing 6 by a flange 11 that is spun into engagement with the inner walls of the casing, as indicated in Fig. 1. The tubular terminal is provided with a bore 12 for receiving a refill, to be hereinafterdescribed.

A threaded terminal sleeve 13 is attached to the closed end of the casing exteriorly thereof and is provided with two flexible and yielding terminal members 14 that extend into the bore 8 through openings 15 in the casing. The terminal members 14 are bent inwardly, as indicated in Fig. 1, and are provided with concave contact surfaces 16 for yieldingly and slidably engaging a contact disc 17 that is part of a thermal-responsive element or refill 18 which includes the contact disc 17 and a heating conductor 19 that is 10:, preferably made of a nickel alloy or other relatively high-resistance metal. One end of the heating conductor 19 is inserted through a perforation 21 in the contact disc 17 and is connected thereto by a small portion of solder 22.

The refill 18 is assembled in the device by inserting it through the open end of the easing in such manner that the inner end of the heating conductor 19 is inserted in the bore 12 of the terminal 9. The flanges 23 of the contact disc 17 slidably engage the concave contact surfaces 16 of the terminal members 11 as the refill is being inserted and cause the surfaces to be cleaned as the refill is moved to assembled position. The yielding terminals 14 insure a good conductive contact between the contact discs 17 and the contact surfaces 16. The refill is retained in assembled relation within the casing by a set screw 21 in the terminal 9 which clamps the heating conductor in the bore 12 thereof.

A tubular heat-absorbing member 25 is disposed within the bore 7 concentric to the axis thereof through which the heating conductor 19 extends. The tube is preferably made of aluminum which, when oxidized, prevents conductive connection between the tube and the heating conductor or the associated contact discs 17. However, the tube may be made of porcelain or other insulating heat-absorbing material. The tube 25 is pressed into engagementwith the contact disc 17 by a helical spring 26 that is disposed between the end wall of the casing and a movable supporting washer 27 upon which the inner end of the tube 25 is seated. The end of the tube in engagement with the contact disc is countersunk to provide a space 28 surrounding the solder connection. The absence of cooling metal in the vicinity of the solder joint insures that the heating conductor will attain its highest temperature at the point of oindcr of the conductor with the contact disc.

lVhen an overload persists for a predetermined time in the circuit in which the thermal-responsive element 18 is connected by means of the terminals 9 and 13, the temperature of the heating conductor at the point of joinder with the Contact disc will rise to the fusing temperature of the solder and re lease the contact discs therefrom. The spring 26 will then instantly force the tube 25 toward the enlarged open end of the casing to the position'indicated in dotted lines. The

tube 25 is moved over the released end of the heating conductor 19 and instantly cools and snulfs out the arc incident to the separation of the contact disc 17 and the heating conductor 19. In fact-,the tube 25 snuifs out the are before the contact disc has become entirely separated from the terminals 1+1.

By reason of this construction, the arc is confined to the point of separation of the contact disc and the heating conductor and no injury to the terminals results. Consequently, the device may be used repeatedly. As a further precaution against heated gases coming into contact with the helical spring 26, the washer 27 is made of such diameter that it closely fits the bore 7 of the casing.

By reason of the presence of the heat-absorbing tube 25, a refill,'that is ordinarily adapted for use in circuits carrying current up to five amperes, may'be used for circuits carrying higher amounts of current, and the time interval at which the cutout operates to open the circuit may be varied by varying the dimensions of the heat-.absorbin tube 25.

The cutout device is also effective for int(.11'tl] )tll1g short-circuits and, under shortcircuit conditions, the temperature of the end of the heating conductor attached to the disc 18 is initially raised to the fusing temperature of the solder because of the absence of heat-conducting metal in the immediate vicinity of the solder joint.

The open end of the casing 6 is closed by a threaded cap 29 having an opening 30 that is closed by a transparent mica disc 31. The disc serves as a stop for the disc member 17 and the device visibly indicates when the circuit has been interrupted. It will be seen from the foregoing that the construction is inexpensive to manufacture and comprises but few simple parts.

In Fig. 4, I have shown a modified construction similar to the construction illustrated in Fig. 1, With the exception that the heat-absorbing tube 25 is attached to the terminal member 9 by means of a threaded neck 32 on the latter member which is screwed into the socket 33 in the inner end of the tube 25. The heat-absorbing tube remains stationary and the contact disc 17 is moved to circuit-interrupting position by an insulating sleeve 3% having a radially-extending flange 35 which closely fits within the bore 7 of the casing 6.

A helical spring 26 serves to force the sleeve into engagement with the contact disc 17 and to move the disc 17 away from the soldered end of the heating conductor 19, when the solder connecting the disc and conductor is fused. The flange 35 protects the spring 26 from the arc gases incident to the interruption of the circuit. The insulating tube 3-1 also serves to confine the arc therein and to protect the terminals 11. As in the previously described device, refills may be repeatedly inserted.

Referring to Fig. 5, I have shown therein a further modification of the device wherein the casing 6 is constructed substantially in the manner shown in my COPQIMliIlQ application previously referred to. In this construction. the refill comprises a contact disc 17 that is soldered to a heating conductor 19 which is retained in the casing in a manner is attached to the sleeve. The flexible strip isconnected to the disc 36 by means of a rivet 39.

A heat-absorbing tube 25 surrounds the heating conductor'l9 and is connected, at its inner end, to a disc 41 which supports a helical spring 42. The springengages an insulating washer 43 that. is disposed between the spring and the inner end of an insulating barrier tube 44 which engages, at its upper end, the inner surface of the disc 36.

When the solder 45 joining the disc 17 and the heating conductor 19 becomes fused, the spring 42 forces the barrier tube 44 outwardly, carrying with it the disc 36 and the contact disc 17. The barrier tube 44 and the disc 36 prevent the rapid escape of arc gases out of the opening 46 through which the extension 38 projects, and the insulating Wash-- er 43 protects the spring 42 from are gases. As in the former device, the device may be repeatedly used by replacing refills after each circuitinterrupting operation.

While I have described and illustrated several embodiments of my invention, it will be apparent to those skilled in the art that various changes, modifications, substitutions,

additions and omissions may be madein the apparatus illustrated Without departing from the spirit and scope of my inventlon, as set forth in the appended claims.

I claim as my invention:

1. In a cut-out 'for electric circuits, the combination with a pair of relatively movable terminal members and athermally-responsive heating conductor releasably connecting the terminal members and adapted to open thecircuitwhen the conductor attains a predetermined temperature, of a heat-absorbing member surrounding the conductor and influencing the heating characteristics of the conductor.

2. In a cutout for electric circuits, the combination with a pair of terminal members and a one-piece composite thermally-responsive member having separable parts releasably engaging the terminal members and joined by a solder fusible at low temperature, of a heat-absorbing member adjacent both said parts and influencing the heating characteristics thereof.

3. In a cutout for electric circuits, the combination with a pair of terminal members and thermal-responsive element comprising a heating conductor connected to one of the terminal members by a fusible member, of a heateabsorb'ing member surrounding the heat.- ing conductor and movable over the end thereof when the conductor has become disconnected from the said terminal.

4. A cutout for electric circuits comprising a pair of terminal members, a thermal-responsive element comprising a heating c'onductor for releasably engaging one of the said terminal members and connected to the other terminal, a heat-absorbing member surrounding the heating conductor and means for moving the heat-absorbing member over the disengaged end of the heating conductor when the latter is released from the first said terminal members.

5. A cutout for electric circuits comprising a terminal, a contact member for engaging the terminal, a heating conductor soldered to the contact member and adapted to be separated therefrom forinterrupting the circuit when the heating conductor attains a predetermined temperature, and a heat-absorbing member surounding the heating conductor and movable over the disengaged end thereof for moving the contact member out of engagement with the terminal member, when the heating member has become disengaged from the contact member.

6. A cutout for electric circuits, comprising a casing having a yielding terminal mem her and a fixed terminal member, a contact member for engaging the yielding terminal detachably connected to the fixed contact member, and a heat-absorbingelement surrounding the heating conductor and movable over the released end thereof for separating -the contact member from the terminal member when the heating conductor is released from the contact member.

7 A cutout for electric circuits comprising a tubular casing having oneend closed and provided with a fixed terminal, a yielding terminal adjacent the open end thereof, a contact disc for slidably and releasably engaging the terminal, a heating conductor detachably connected to the contact disc and responsive to current therein for releasing the contact member, means for detachably connecting the heating conductor to' the fixed terminal, a movable heat-absorbing member adjacent the heating conductor and means for moving it for separating the said contact member from the heating conductor when the former is released. I

8. A cutout for electric circuits comprising a tubular casing having one endclosed and provided with a fixed terminal, a yielding terminal Within the casing, a thermal-responsive refill having a contact member releasably engaging the yielding terminal and a heatmember out of engagement with the yielding terminal having a portion closely fitting the for obtaining a time inner walls of thecasing for protecting the spring from are gases incident to separation of the contact member and heating conductor.

9. The combination, in a fuse cutout, of insulating means for supporting a pair of terminals, a fuse element comprising a heatconducting member soldered to a *releasable member, means for releasably supporting the fuse element across the terminals, and heatabsorbing means adjacent the fuse element lag in the operation of the cutout. l

10. In combination with a fuse cutout comprising an insulating casing and a pair of terminals, of a composite renewable fuse element comprising a heat-conducting element soldered to a current-conducting member, means for releasably supporting the fuse element across the said pair of terminals, and

means adjacent to the fuse element for producing a time lag in the operation of the cutout. r

11. In combination with a fuse cutout comprising an insulating casing and a pair of terminals, of a composite renewable fuseelement, comprising a heat=conducting element soldered to a current-conducting member, means for releasably supporting the fuse element across the said pair of terminals, and means adjacent to the fuse element for producing a time lag in the operation of the out out, said time lag being in inverse proportion to theincrease in current in the circuit.

In testimony wherof, I have hereunto subscribed my name this 9th day of January, 35

MAURITS J. SANDIN. 

